Removable fluid impingement starter nozzle construction for turbo-engine



Jan 9, 1962 T. F. LAWRENCE ET AL REMOVABLE FLUID IMPINGEMENT STARTER NOzzLR CONSTRUCTION FOR TURBO-ENGINE Filed March 16, 1959 IN V EN TOR5. #was f misa/v r//a/w E mma-m? irl-VINAV- United States Patent f() 3,016,227 REMOVABLE FLUID IMPINGEMENT STARTER NOZZLE CONSTRUCTION FOR TURBO-ENGINE Thomas Frederick Lawrence and James Frederick Ingleson, Beverly, Mass., assignors to General Electric Company, a corporation of New York Filed Mar. 16, 1959, Ser. No. '799,602 2 Claims. (Cl. 253-78) This invention relates to fluid impingement starters for turbo-engines, and more particularly to a removable iluid impingement 'starter nozzle construction for aircraft gas turbine engines.

In many applications of turbo-engines, it is desirable to reduce the diameter of the engine installation to a minimum. This is especially desirable in aircraft, so that the engine can be fitted into a nacelle of small size and consequently low air drag. Many installations in aircraft fuselages also require minimum engine diameter, especially in the case of guided missiles. v

f For this reason, fluid impingement starters, of the type comprising a nozzle spaced radially and exteriorly of a turbine engine casing to impinge a stream of compressed air or other fluid on a turbine rotor, have not been desirable in installations of such limited dimensions. Furthermore, the necessity for carrying a compressed fluid supply or a separate air compressor to operate such a starter, adds another penalty to the weight and installation space represented by such a starter.

It is an object of our invention to provide in a turboengine adapted to receive a removable iluid impingement starter nozzle, means for enclosing a starter nozzle-receiving opening in the engine casing to prevent the escape of working fluid therefrom during normal running subsequent to starting thereof.

We have found that a satisfactory fluid impingement starter may comprise a iluid nozzle insertable into an arcuate opening in a turbo-engine casing and a mating opening in a conventional shroud ring, which circumferentially encloses the blades of the turbine rotor. The nozzle may be inclined from the radial direction so that the air stream impinges upon the buckets tangentially of the rotor. However, Whether the nozzle is ilXed or removable, the arcuate opening in the shroud ring defeats the purpose of the latter to some degree, since leakage flow of working lluid past the tips of the turbine blades during normal operation of the turbine engine results, with consequent loss of useful work extracted from the fluid.

The use of compressed air of relatively low pressure (in the order of 4 atmospheres or less) is desirable in a starter of this kind, because of the relative simplicity, safety, low cost, and weight of a source supplying such relatively low pressure air. However, the starting torque developed in the turbine depends upon the mass rate of flow as Well as the pressure of the fluid supplied, so that the cross-sectional area ofthe. starting nozzle and the mating shroud ring opening must be correspondingly increased for relatively lower pressures. This increases the magnitude of Working iluid leakage past the turbinejblades during normal operation of the engine.

It is a further object of our invention to provide in a turbo-engine adapted to receive a removable fluid impingement starter nozzle, means for preventing radial leakage llow of working iluid around a turbine through a starter nozzle-receiving opening in the engine.

Other objects and advantages of our invention will become apparent as the description proceeds. v

Briefly stated, in accordance With one aspect thereof, our invention may be carried out byproviding a starter nozzle mounting pad formedwith a duct and secured tothe casing of a turbine engine at a` point radially spaced from the turbine rotor, together with a fluid impingement starter nozzle removably received in the duct in iluid communication with the rotor. The turbine rotor is circumferentially enclosed by a shroud ring partially delining a working fluid passageway therethrough, and aligned arcuate openings are formed in the casing and in the shroud ring to receive the fluid impingement starter nozzle. The nozzle is removably secured in the mount' ing pad by any suitable means, and directs starting iluid supplied through a conduit from a compressed fluid source, radially and tangentially into the blades of the turbine rotor. A cover member is provided with a cover plate for enclosing the mounting pad upon removal lof the starting nozzle to prevent the escape of Working fluid from the engine, and preferably is-provided with an arcuate ring segment which mates With the arcuate opening in the shroud ring .to fully enclose the gas path dened by the shroud ring and prevent'radial leakage flow of working'iluid around the vturbine rotor during normal operation of the engine.

While the cover plate may beplaced on the mounting pad manually after removal of the starting nozzle, it is preferable from the standpoint of safety to provide a suitable linkage for moving the cover plate into position, because of the danger from hot working fluid escaping through the arcuate openings in the shroud ring and casing during this operation.

With the cover plate in position during normal engine operation and in flight, restarting may be accomplished by fwindmillingf or by' providing other starting means.

forming part of the permanent installation, such as an electric starter.

In installations utilizing other starting means, such as an electric starter, the cover plate may be permanently left in place on the mounting pad, so that the same casing structure may be utilized in such installations.

A While the specification concludes with claims particularly pointing. out and distinctly claiming the subject matter which We regard as our invention, it is believed that the invention may be more clearly understood from the following description of a preferred embodiment, referring to the drawings, in which: f

FIG. 1 is a fragmentary cross-sectional View of a turboengine incorporating a preferred embodiment of our nozzle construction;

FIG. 2 is a fragmentary view in perspective of the starter nozzle of FIG. l; Y

V FIG. 3 isa fragmentary view in perspective of the engine of FIG. 1, with the starter nozzle removed;

` FIG.` 4 is a view in perspective of a cover member for the Vnozzle construction and a portion of an operating linkage therefor; and

FlG. 5 is a view similar to' FIG. 1, but showing the cooperation of the cover member with the turbo-engine.

In the drawings, a turbinev rotor comprising a circumferential row of turbineblades 1 forms an elementrof an internal combustion turbine engine. The engine includes working fluid generation means of any suitable type (not shown), forming no part of this invention, for supplying working fluid to blades 1. The turbine rotor is rotatably mounted within a casing 2. A gas path for conducting the working fluid from the generation means through the turbine is partially defined by a shroud ring 3,circum ferentially spaced about blades 1 to minimize leakage ilow of working fluid past the tips 4 thereof. Blades 1 are constructed and arranged'V to be driven in the direction shown bythe arrow by the passage of working fluid therethrough, in a manner Well known to those skilled in the art.

In order to rotate Iblades 1 of the rotor to start' the turbo-engine, We provide a starting nozzle 5 connected by means of a suitable conduit to any desired source of compressed iluid (not shown), forming no part of this invention. Any well-known source capable of delivering uid at a mass rate of flow and under a pressure sufficient to rotate the turbine rotor at starting speed may be used. We prefer to use a fluid supply under a pressure of about 4 atmospheres or less, in the interests of simplicity, safety, and economy of the source.

Nozzle 5 is formed with a passageway 6 in lluid communication with the compressed iluid source through the conduit previously mentioned. The nozzle may be shaped in a mann-er suited to the particular application, as is well known in the The convergent curved form shown is by way of illustration only.

A mounting pad 7 is formed asa radially extending projection of casing 2, and is formed with an internal duct 8 removably receiving nozzle 5 therein. Mounting pad 7 is further provided with a peripheral flange 9 at its radially outer extremity, for abutment upon a cooperating ange 10 peripherally formed about nozzle 5 to support the nozzle upon the mounting pad. (See FIGS. 1 3.) Flanges 9' and 10 are preferably so positioned on pad 7 and nozzle 5, respectively, that compressed uid flows from the nozzle into turbine blades 1 in a direction having radial and tangential components; this improves the angle of impingement of the liuid upon the blades to give a more effective reaction, in a manner well known in the art.

Casing 2 and shroud ring 3 are formed with mutually aligned arcuate openings 12 and 13, respectively, situated within the connes of duct S to receive tip portion 14 of nozzle 5 therethrough. Tip portion 14 is formed with a curvature corresponding to the periphery of rotor 1, in order to direct starting fluid most effectively into bladesv 1. As best seen in FIGS. 2 and 3, arcuate openings 12 and 13 and nozzle tip 14 are preferably of rectangular shape, to extend circumferent-ially over the tips of one or more blades 1, and axially over a portion of the blades. The starting uid thus impinges over the blades to produce useful reaction torque with a minimum of leakage upstream or downstream thereof. Nozzle Sis formed with a gradual and smooth transition from a circular cross-section at its inlet portion, to the rectangular configuration of tip 14.

In order to removably secure nozzle 5 in operative position for starting the turbo-engine, upon mounting pad 7, suitable means for securing flanges 9` and 10 in abutting relationship are provided. We prefer to employ a split clamping ring generally designated 16, of a well-known and commercially available type; however, any quickly removable fastening means may be utilized for this purpose. Clamping ring 16 includes a split Vband 17, comprising an oval split ring conforming to flanges 9 and 10. Flanges 9 and 10 are chamfered at 9 and 10', respectively, to receive V-band 17, which is spread and slipped over the flanges in assembled position. The clamping ring further includes a split band 18 peripherally spaced about V-band 17, and spot-welded or otherwise secured thereto at 19. Band 18 is split a-t a point diametrically opposite weld 19, and is formed with spaced apart parallel lips at the edges of the split, one of which is shown at 20. After the clamping ring has been spread and slipped over flanges 9 and 10, a screw 21 is threaded through lips 20, and is drawn up to contract V-band 17 into clamping engagement with the anges. The V-section configuration of band 17 serves to draw anges 9 and 10 into snug sealing abutment. In order to insure more complete sealing of the joint, we preferably place a resilient O-ring seal 22 in a sui-table annular groove 23 formed in flange 9 about duct 8, the groove being of somewhat less depth than the thickness of the O-ring. The Oring is deformed in sealing engagement with flanges 9 and 10 as screw 21 of clamping ring '.16 is drawn up.

After starting of the turbo-engine, screw 21 is threaded out of lips to permit expansion and removal of clamping ring 16 and removal of nozzle 5 frommounting pad 7. The nozzle and the associated conduit and starting fluid source may then be left on .the ground as the aircraft carrying the engine installation takes flight. The nozzle and fluid source may conveniently be carried by a ground cart.

In order to prevent the escape of working fluid from blades 1 throughv openings 12 and 13 and duct 8, after removal of nozzle 5 and during normal running of the engine, we provide a cover mem-ber for the duct, which includes a cover plate or mounting portion 25 as shown in FIGS. 4 and 5. Cover plate 25 is shaped toy conform to flange 9 of mounting pad 7, and is secured thereto by means of clamping ring 16, or other suitable fastening means, after starting of the turbo-engine and removal of nozzle 5.

While cover plate 25 serves to prevent the escape of Working fluid from the engine, it cannot alone prevent the loss of useful work resulting from the radial leakage of working iluid into duct S through openings 12 and 13,

radially outwardly of the tips 4 of blades 1, and radiallyV back into the blades at the downstream edge of the blades. It should -be noted that this leakage llow would also occur if the fluid impingement starter nozzle were fixed in place, and not made removable in accordance with our invention. Such a leakage ilow, and the resulting disturbance of the flow pat-tern of working fluid thro-ugh the blades, would cause a substan-tial loss in the extraction of useful work from the working uid bythe turbine.

This problemis aggravated as openings 12 and 13 are increased in size. However, we have found it desirable, as previously explained, to use relatively low pressure starting fluid, e.g., about 4 atmospheres of pressure, or less. A relatively large area nozzle is consequently required -to obtain an adequate mass rate of flow of starting uid to drive the turbine at starting speed; and open ings 12 and 13 must be made correspondingly large.

IIn order to lprevent the radial leakage flow of working fluid into du-ct 8 and around blade tips 4 during engine operation, we provide an arcuate ring segment or member 26, shaped to ll opening 13 and conform to the curvature of shroud ring 3. The arcuate ring segment is carried by cover plate 25 upon a web plate 27, welded at opposite edges 28 and 29 to the arcuate ring segment and the cover plate, respectively. Cover plate 25 thus supports arcuate ring segment 26 within arcuate opening 13, so as to substantially complete shroud ring 3, when the cover plate or mounting portion 25 of the cover member is in position on mounting pad 7. As will be apparent from the previous explanation, the working fluid leakage loss prevented by utilizing arcuate ring segment 26 is relatively greater in applications using relatively low starting fluid pressures. The same leakage loss would obviously occur if the starting nozzle were permanently fixed in place and not made removable.

While cover plate 25 may be positioned on mounting pad 7 manually or by means of hand tools, it may be desirable from the standpoint of the safety of persons performing this task to provide mechanical means to assist -in the positioning. We therefore prefer toy provide an arm 30 for manipulating the cover plate. Arm 30 is secured by rivet 3'1, or other suitable fastening means, to the surface of cover' plate 25. Arm 30 may be handled manually, may be pivoted at -an opposite end thereof to rotate the cover plate into position, or the cover plate maybe handled by any other suitable means, such as will occur to those skilled in the art.

In engine installations utilizing other starting means exclusively, such as an electric starter, cover plate or mounting portion 25 may be secured in place on mounting pad 7 by means of clamping ring 16, or other suitable fastening means, and left permanently in position. In other applications, it may be desirable to use a uid impingement starter for testing of engines during manufacture, and thereafter to close up the mounting pad permanently by means of a cover plate. Our invention thus permits completely exible utilization of a single casing confor turbo-engines, in which a starter nozzle and a sourcel of starting fluid therefor may be removed rom an engine installa-tion subsequent to the starting opera-tion, 'and including means for enclosing nozzle-receiving openings in the engine to eliminate lWorking fluid leakage losses and escape during norma-l running of the engine. It should be understood that our invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that modiiications may occur to those skilled in the art Without departing from the spirit and scope of our invention.

What We claim as new and desire to secure by Letters Patent of the United States is:

1. The combination in a turbo-engine of a cylindrical casing, a turbine rotor having a circumferentially-spaced row of turbine blades mounted in said casing for rotation about an axis, rsaid casing circumferentially spaced about said blades in proximity to the tips of said blades and formed with an opening extending circumferentially about and axially along said blades over an arcuate portion of said casing, a mounting pad secured to said casing about said opening therein, a cover member including a mounting portion and an arcuate ring segment, -said mounting pad constructed and arranged to receive a removable uid impingement starter nozzle in fluid communication IWith said blades through said opening and to receive said cover member upon removal of said nozzle from said mounting pad, and -means to secure said mounting portion of -said cover to said mounting pad, said arcuate ring segment substantially iilling said opening in said casing and extending into proximity to the tips of said blades When said mounting portion is secured to 4said mounting pad to oppose r-adial leakage of uid through said opening in said casing. v

2. The combination in a turbo-engine of a cylindrical casing, a cylindrical shroud ring, a turbine rotor having a oi-rcumferentially-spaced row of turbine ybla-des mounted in said casing for rotation about an `axi-s, said shroud ring circumferentially spaced about said blades in proximity to the tips of said blades and formed with an opening extending circumferentially about land axially along said blades over an arcuate portion of said casing, said casing circumferenti-ally spaced about said shroud ring and formed with an opening aligned with the opening in said shroud ring, a mounting pad secured -to -said casing about said opening therein, 'a cover member including a mounting portion and an arcuate ring segment, said mounting pad constructed and arranged to receive a removable fluid impingemeut starter nozzle in fluid communication with said blades through said aligned openings and to receive said cover member upon removal of said nozzle from said mounting pad, and means to secure said mounting portion of said cover to said mounting pad, said arcuate ring segment substantially filling said opening in said shroudring and extending into proximity to the tips 0f said blades t-o form `a substantially continuous surface with -said shroud when said mounting poi-tion is secured to said mounting pad to oppose radial leakage of uid through said opening in said shroud ring.

References Cited in the file of this patent UNITED STATES PATENTS 

